This invention relates to a circuit for producing true differential line reception for a differentially driven tri-level signal.
Tri-level bipolar signals are often transmitted over a pair of lines. Such signals have no DC component and require relatively narrow bandwidth; however the transmission lines add noise. The receiver recovers and processes the bipolar signals to reproduce the transmitted data.
Various circuits have been used for recovering and processing such bipolar signals. Typical are the circuits shown by U.S. Pat. No. 3,894,288 to Musser, Jr.; 3,518,560 to Auiqnon and 4,007,382 to Warberg. This and other prior art use DC biasing techniques that compare each signal line to a locally generated DC bias. This technique degrades the signal to noise ratio, while eliminating any common mode noise rejection. It is an object of the present invention to provide a simple and true differential line receiver for differentially driven tri-level signals. Another object of the present invention is to provide an improved circuit for receiving and separating a differential tri-level serial data stream and converting the received serial data stream into data and clock for use with standard bi-level logic. Another object is to provide improved input biasing of differential tri-level inputs to permit a true differential comparison and signal detection. Another object is to provide high common mode rejection of noise that is developed during transmission.